Cities for Climate?

Unless you think climate change is alt.news manufactured in China, you realize that our steady march towards +2 degrees or more is no longer a scientific question or even a technological challenge, but a political problem. If so, a question arises: what's the right framework for a political solution? Let me offer three choices: 

1. International agreements such as the Paris accord after COP21. We clearly needs these but I wonder about the signal to noise ratio - how much is posturing and how much is genuine commitment? Plus, they aren't binding as we are finding out in the US of A. 
2. National policies. Same problem as above: who's going to keep the politicians accountable? Plus, do we need large bureaucracies to manage our transition to a green society? 
3. Cities. My favored solution. Why? Because most people live in cities and dense urban lifestyles are simultaneously greener (if you look at carbon footprint per capita) and more wasteful - if you look at the carbon footprint of the supply chains that feed, clothe, transport and power people in cities. At the same time, because cities are tangible and physical, there's a direct feedback loop between policy and action. Climate action in cities can directly engage civil society, business and government and hold them to their commitments in (almost) real time. Finally, most of humanity lives in cities and that number is only going to increase. 

So should we focus on climate action efforts on cities?